Fusion generator of high intensity, pulsed neutrons



Aug. 29, 1967 w, L. FINK 3,338,789

FUSION GENERATOR OF HIGH INTENSITY PULSED NEUTRONS Filed Aug. 20, 1965 4 Sheets-Sheet 1 I l lmll ll lh "31v llllm ull 4.

' WILLIAM L. FINK INVENTOR w MM ATTORNEY Aug. 29, 1967 w. L. FINK 3,338,789

FUSION GENERATOR OF HIGH INTENSITY. PULSED N EUTRONS Filed Aug. 20, 1965 4 Sheets-Sheet 2 A 234 as 212 l4 Mev. switch a ark PI neulr 7 5 I qgp sw. electrodes tarqeqson WILLIAM L'FINK pulse INVENTOR. I F I G. 4

ATTORNEY Allg- 29, 1967' w. L. FINK 3,338,789

FUSION GENERATOR OF HIGH INTENSITY, PULSED NEUTRONS Filed Aug. 20, 1965 4 Sheets-Sheet 5 WILLIAM L. FINK INVENTOR.

EWM

ATTORNEY Aug. 29, 1967 W. L. FINK Filed Aug. 20, 1965 4 Sheets-Sheet 4 To 636 NEUTRON GENERATOR TO VACUUM 638 632 TO 624 PLASMA FLAW i ELECTRODES OF E NEuTRoN GENERATOR B: s2 5 .3 TRIGGER DELAY ADJUST Y PULSE TRANSFORMERS 630 U: TO

NEUTRON INTERNAL L T GENERATOR DELAY 6 ADJ ST U i -f---f--i- 639 634 PlNCH TARGET /%LIELECTRODE To VACUUM T t 6 2 TO NEUTRON GENERATOR 6 3 6 6'4 FIG. 6

WILLIAM L. FINK INVENTOR.

/ADAM ATTORNEY United States Patent 3,338,789 FUSION GENERATOR OF HIGH INTENSITY, PULSED NEUTRONS William L. Fink, Fort Worth, Tex., assignor to General Dynamics Corporation, Fort Worth, Tex., a corporation of Delaware Filed Aug. 20, 1965, Ser. No. 481,350 1 Claim. (Cl. 176-5) energizing it to produce an ultra-high effective beam current of ions, thus propelling it at a high velocity into sorbefacient impact with a pinched-plasma target of isotopic gas.

In the preferred form of the invention, this is accomplished by employment of a composite neutron generator structure comprising an electromagnetic, coaxial-rail, deuterium plasma flaw propagator/accelerator in communication and operatively associated with a tritium ion vapor producing, magneto-hydrodynamic, plasma-pinch target chamber, thereby effecting the useful release of 1 mv. neutrons by the fusion reaction H (H ,n)He

In the contemporary art, processes and devices of this class which employ the leuterium-tritium fusion process have been severely limited in deuterium ion currents be cause of severe space charge problems in the ion accel erator and because of secondary electron depletion of stored energy systems. One of the more material limitations in the prior art, however, has been the relative high rate of energy loss. This is the energy which incident ion beams give up in ionizations of electrons'in collisions with a target; particularly where such target is a solid medium. 'In such systems attempt is made to separate the electrons from the deuterium ions, then accelerate the ions into a tritium-bearing target assembly.

Further disadvantages of the present state of the art reside in the inherent complexities which are characteristic of these systems, giving rise to extreme difliculties in achieving control for focusing and directing the ion beam into the target;

The present invention overcomes these and other deficiencies of the prior art in that the deuterium ions are herein accelerated as an ion plasma with a moderate separation of the electrons and ions. Both electrons and positive ions are accelerated in the same direction, thereby eliminating the space charge deficiency of the prior art. For this reason an effective ion current in thehigh kiloampere region is produced. In the proferred embodiment the plasma target is utilized in conjunction With a pinch discharge in a tritium gas or a deuterum-tritium gas mixture to provide a new and improved means for effecting much higher concentrations of tritium ions in the central region of the pinch and consequently into the target area.

An additional advantage is gained through such employment of the pinch target in that the electrons are pro-ionized and are thus boosted to sufficiently high energies that they materially reduce the energy losses of the incident plasma of deuterium.

In recent years the character, chemical nature and utility of deuterium, D or H has become well known to those skilled in the art. Deuterium, being an isotope of hydrogen, has a mass number of two; its nucleus comprises one proton and one neutron. Further, the character, chemical nature and usefulness of titriumhas become equally well known. Tritium, T or H is also an isotope 3,338,789 Patented Aug. 29, 1967 radioactive and radiates beta particles, yielding helium factually established that such is the case.

It is one object of the present invention to provide a manufacture, easy to operate and versatile in its application to useful ends.

These and other objects, features and advantages of plasma flaw propagator/accelerator component and a magnetohydrodynamic pinched-plasma target component. FIGURE 2 1s an elevational View in cross-section of FIGURE 4 is a block diagram, schematically illustratmg the power supply, electromagnetic systems and magmete-hydrodynamic pinch-plasma target as employed for :he fusion generation of neutrons in the present invenion.

FIGURE 5 is a truck ponents, and

FIGURE 6 is a schematic block diagram showing the functional relationship and arrangements for the electrical, vacuum and fuel gas auxiliary systems employed in the mvention.

Referring now to FIGURE 1 of the drawings, the preferred embodiment of the invention is shown as a composite fusion neutron generator 10, comprised generally of a plasma propagator component 20 and of a magnetohydrodynamic pinch-target, fusion chamber component 30; the former component 20 functioning both as a plasma producing ionization chamber 22 for an isotopic gas fuel and as its related coaxial-rail plasma flaw 24 accelerator and the latter functioning both as a fuel gas ionization chamber 43 and its related magnetohydraulie pinched plasma target producing medium 46. Component 20 is composed of a cylindrical outer electrode 26 and 9. cylindrical inner electrode 28 having an orifice 29 in communication with passageway 34 and positioned in concentric relationship, and passing through disc-like insulation end plate 32; thus projecting well into the center of chamber 22 of component 20. A suitable fusionable' isotopic gas such as deuterium is introduced into chamber 22 from a conventional puff-gas system (FIGURE 6) through orifice 29 (FIGURE 1). The gas systems which supply deuterium and tritium to the present composite neutron generator are essentially identical for the plasma flaw chamber 22 and for the pinch target chamber 43. As shown in FIGURE 6 such systems are comprised of a gas bottle or cylinder container 610 preferably containing deuterium or a deuterium-tritium mixture or tritium, a shock actuated gas-puff valve 612, a controlled leak valve, and a regulator (not shown). In the case of tritium, a leak detector and closed cycle gas recovery system connected to the vacuum pump exhaust is preferably employed.

Again referring to FIGURE 1, chamber 22 is defined by cylindrical outer electrode 26 and essentially functions as an electric arc plasma gun in that fusionable deuterium gas upon being introduced thereinto is ionized by an arc discharge from electrode conduit 28 to electrode 26 and the deuterium ions are accelerated as an ionized plasma flaw 24. It is to be particularly noted here that the rail accelerator has the effect of propelling both electrons and positive ions in the same direction, thereby substantially eliminating any space charge limitations. Ionization and electrodynamic acceleration is effected by a conventional high voltage electrical discharge system as shown in FIG- URE 6. A power supply and energy storage bank are employed for both plasma flaw chamber 22 and the disc electrode 36, defining a linear pinch-plasma target chamber 43. Each high voltage power supply employs a trigger spark gap 616618, FIGURE 6 and a trigger capacitor 620-622. Trigger signal generation and sequence timing for each system utilize trigger signal generator, trigger variable delay unit 626, trigger amplifiers 628 and delayed trigger amplifier 630 and pulse-forming high voltage units 632 and 634. A single master trigger generator 624 is sufficient for dual operation of the two systems.

Inasmuch as the plasma gun function of chamber 22, FIGURE 1, and that of linear pinch plasma target chamber 43 operate below atmospheric pressure initially, a mechanical vacuum pump (not shown), diffusion pump and a liquid nitrogen cold trap system of conventional design are employed. The mechanical and diffusion pumps are capable of pulling a relatively high vacuum and a liquid nitrogen cold trap is employed to condense hydrocarbons which come from the pump. Each vacuum system is suitably monitored by an alpha ion gauge 636, FIGURE 6, to determine vacuum pressure.

When the stored electrical energy is released at 638 (FIGURE 6), and initiated through 38 (FIGURE 1) through a low pressure gas, such as deuterium, within chamber 22 the spark discharge creates a deuterium plasma sheet flaw 24 between electrodes 28 and 26. The rising current between such electrodes induces a very rapidly rising magnetic field whose interaction with the current induces a strong accelerating force 40 on the plasma flaw 24 in a direction parallel to the longitudinal axis of the plasma flaw accelerator compartment 22. Axial plasma velocities on the order of cm./ sec. are thus achieved.

Substantially simultaneous to the above, a tritium gas is introduced at inlet orifice 42 (FIGURE 1) and is thus received and contained in cylindrical target chamber 43, the end disc walls of which function as a positive second voltage electrode 36 and a ground electrode 44 respectivey- A high voltage a e is in iated at 39, which arcs between these two electrodes by discharge from the capacitor banks previously described, ionizing the tritium to form plasma 48. A rapidly rising electron current in the target plasma pinch discharge chamber 43 gives rise to an azimuthal magnetic field 46, which inwardly pinches ionized gas plasma 48 toward the longitudinal axis of chamber 43. This action simultaneously increases the electron temperature and also increases ion-density along this axis for the duration of the pinch.

Introduction of deuterium plasma flaw 24, accelerated to a very high velocity into the linear pinched axial region of tritium gas plasma 48 results in a high sorbefacient impacting of the deuterium ion flaw 24 into the densified tritium ions, thus producing the desired 14 mev. neutrons as hereinabove described. It will therefore be readily apparent to those skilled in the art that by the combination of the ionization/ acceleration component 20 with linear pinched-plasma target component 30 to provide a composite fusion neutron generator 10 for producing 14 mev. neutrons, the two major limitations of conventional processes and related apparatus are overcome, i.e., the severe space charge problems inherent in conventional ion accelerators and high rate of energy loss which incident ion beams experience in the ionization of electrons in collision wtih a target. Further, the problem of secondary electron current depletion of stored energy systems employed by devices of the prior art is substantially eliminated by use of this new generator 10.

A second embodiment which employs simple parallel rail electrodes as the plasma accelerator rather than coaxial rail electrodes and a sorbefacient solid plate or disc interstitially containing the f-usionable isotopic gas is ilustrated by FIGURES 2 and 3. In such embodiment, parallel copper electrode rails 210 and 212, FIGURE 2, are mounted on the upper 214 and lower 216 innerfaces of vacuum ion chamber 220; said chamber being defined by a closed cubicle structure 218, which is made of an electrical insulator material, such as glass or commercial Lucite. An integral end closure 222 is provided to seal one of its ends. At the opposite end there is provided a disc target receptacle 224 having a central aperture 226 and shoulders 228 which are received into this end of chamber structure 218 to provide a fitted assembly therewith. The inner faces 230 and apertured shoulders 228 are arcuately shaped so that shoulder portion 228 is brought into concentric registry with aperture 226 and :disc target 232 when assembled. Disc target 232 is of conventional solid target construction, such as a zirconium faced copper plate; the zirconium of which is interstitially infused with tritium gas or other suitable fusionable isotopic gases. End retainer plate 234 has an arcuate groove 236 near its outer edge for receiving resilient O-ring 238 which serves to seal target 232 when end plate 234 is attached to receptacle 224 by any suitable means, such as bolts, which are passed through a plurality of apertures 240 about the outer periphery thereof. Disc target 232 is permitted to float electrically during the capacitor bank discharge. Valved conduit 246 serves for the evacuation of air from the chamber defined by cubicle structure 218 and for the introduction of a fusionable gas thereinto by suitable connection to aperture 248.

In operation, the capacitor bank, previously described, is charged to the desired high voltage (on the order of 10,000300,000 volts) by the charging power supply; the capacitor bank being connected to the rail accelerator electrode 210 at connector 242 through a conventional spark gap switch 244 in a manner similar to that of the preferred embodiment, heretofore described. Upon command from the switch trigger 244, energy stored in the capacitor bank is discharged into the plasma accelerator electrode 210 and an ionizing arc passes to electrode 212 through the deuterium or other isotopic gas and a plasma is formed and axially accelerated to the required velocity in the direction of target 232, When the deuterium plasma impacts such target and is dynamically interspersed into the tritium gas interstitially permeated therethrough, fusions occur by the H (H ,n)He reaction and monoenergetic 14 mev. neutrons are released in a short-duration, high intensity burst. The fusionable isotopic plasma gas may, in a modified form, be encapsulated as shown in FIGURE 2. Here, capsule 310 is made of a conducting material, such that when a high voltage are is applied both capsule and gas are ionized and are accelerated toward the target. In this form the plasma chamber is perated in an initial vacuum. A graphic schematic, in block diagram form, which serves to illustrate the system arrangement for the above described process, is shown in FIGURE 4.

Useful applications of the presently invented process and apparatus are many fold and varied; exemplary uses include relatively large capital plant fusion generators for the purpose of advanced radiation effects studies on a large scale, such as in radiation effects technology relating to relatively large masses for determining both permanent damage and transient effects on object irradiated materials and matter. Further, neutron induced ionization technology and related transient phenomena may be investigated and advanced with the availability of such facilities.

A smaller, simplified embodiment such as shown in FIGURE 5 of the drawings and hereinabove described have many applications as scientific instruments and are very useful for purposes of classroom instruction .and laboratory investigations in universities and secondary schools. Exemplary of such use, the small scale fusion neutron generator of FIGURE 1 is mounted on a compartmented truck composite 510, such as shown in FIGURE 5. Castors 512 prov'de convenient mobility While readily accessible compartments therein contain the required banks of capacitors 514 and related electrical equipment such as power supply connections and triggering devices. Necessary plasma fuel gas bottle 518 and target fuel gas bottle 516 .as well as vacuum pump 520 and related vacuum system such as illustrated by FIG- URE 6 are also provided for in suitable compartments.

From the foregoing, it should be clearly apparent that other alternate embodiments of the invention may be readily employed by those skilled in the art without departing from the spirit and scope of the invention as herein set forth. For example, numerous fusion fuels other than deuterium and tritium gases may be employed. Further, various other targets and target arrangements are within the scope of the invention such as a colliding plasma target or a slanted solid target plate. Other known forms of co-axial and parallel or non-parallel rail electrodes may be utilized for propagation and acceleration of the plasma flaw and magnetohydrodynamic constriction of target plasmas.

Accordingly, it is to be expressly understood that the spirit and scope of the invention is to be limited only by the scope of the appended claim.

I claim:

A- fusion neutron generator device for the release and high intensity, pulsed emission of monoenergetic neutrons, comprising in combination:

(A) a composite, compartmented structure defining sealable and at least partially evacuated first and second chambers which are in open, unrestricted communication with each other and respectively capable of receiving separately injected fusionable fuel gases thereinto;

(1) at least one elongated wall structure defining said first chamber and a second wall closing one end,

(a) said elongated wall functioning as one electrode of a plasma generating and propelling system and effective to accelerate a projectile plasma into a target at high velocity,

(b) said second wall receiving therethrough a substantially tubular fluid conduit means selectively openable to the interior of said first chamber, said conduit also being selectively and sequentially operable as a second electrode of said generating and propelling system to thereby admit a fusionable fluid fuel into said first chamber and thus into a reaction zone between said electrodes, the voltage discharge between said electrodes ionizing the thus admitted fusionable fluid fuel to form a plasma while the rapidly rising electron current between the electrodes produces a very fast evolving magnetic field and resultant interaction with said voltage current inducing a very strong linear propelling and accelerating force to said plasma,

(2) said second chamber defined by a plurality of walls, at least one of which is functionable as a positive electrode and at least one of which serves as a ground electrode for a plasma propagation-pinch densifying system,

(a) at least one of said walls receiving a gas conduit therethrough, operative to selectively admit a fusionable gas fuel to said second chamber in a programmed timesequence manner relative to the time of gas injection into said first chamber,

(3) said second plasma propagation-pinch densifying system operative to densify and shape the electrical discharge heat-generated plasma into a pinched plasma target,

(4) said densified pinched plasma target resultant in ultra-high energy neutron release and pulsed emission from said target upon sorbefacient impact of said first chamber accelerated-projectile plasma.

References Cited UNITED STATES PATENTS REUBEN EPSTEIN, Primary Examiner. 

